Piston-ring.



M. L. DUNHAM. PISTON RING.

APPUCATION FILED APR. 18.1916.

Patented Oct. 2, 1917.

3311 4;, (1H0: new a g UNITED STATES PATENT OFFICE.

MILLABD L. LD'UII'IALI, Cl iv'E'l-E' EC-RH, H. Y., ASSIGNOR 0F ONE-FOURTH TO LOUIS or: F. MUNGER, 0F NE YORK, N. Y.

PISTON-RING.

Specification of Letters Pa Lent.

Patented Oct. 2, 1917.

Application filed April 18, 1916. Serial N0. 91,854.

T 0 0H whom it may concern Be it known. that i, BZIILLARD L. DUNHAM, citizen of the United and resident oi the borolmh oi liiauliattiuz, in the city, county, and tats of New York, have invented certain new and useful Improvements in Piston-Rings, of which the following is a specification.

This invention relates to piston rings, and consists in a certain method of treatment, or ste in the manufacture of piston rin s, whereby theserdevices are rendered more ellicient and serviceable in the performance of the functions for which they are designed.

Piston rings are usually made from cast iron, and rey for their outward tension, whereby gas tight relationship with the cylinder wal is provided, upon the inherentelasticity of the material from which cost,

in the restoratory effort toward resumption of their original contour; after the inward compression to which they must be subjected in order to introduce the rings, upon a piston, within the c linden Thus the rings are usually cast 0 a diameter great-er than the inside diameter of the cylinder with which they are to be used, and are split F at one point, by the removal of a portion of the ring material, leaving two opposed ends, to provide space for the aforesaid inward compression; the s ace being of such extent only that when a ridged. by the inward compression for service, the opposed ends will have spaced relationship just sufiicient to servel'the purposes of heat expansion and contraction in use.

A true bearing outwardly cannot be as sured with a piston ring .which has been singly cast or machined larger than cylinder size, and a section removed to allow compressing to operating size, to secure the necessar tension. Nor will it serve to re-turn the mug when contracted. Rings thus ordinerily roduced wiil not always assume the form 0? a true circle when fitted to a cylinder, and a positive bearing of flie -ring cannot be obtained againstthe cylinder wall.

Under this ordinary method of piston ring manufacture the true circular form, becomes distorted when the ring is contracted to fit within the cylinder; the distortion consisting, in portions of the ring, near its ends, lagging inwardly, learing clearances between the outer peripheral surface said 55 portionsover certain arcs-and the opposed. portions of the cylinder wall. Those clearances permit suilicicnt leakage to aii'cct the cylinder compression.

Various means hare been sought to rectify this deficiency in piston rings, and my present inver rtion is directed to a novel, simple, and efficacious method, whereby a circular ring, produced in the ordinary 'wa y, is caused to have a true circular cont-our after it has been contracted to fit withiua cylinder.

This method, briefly stated, consists in first cutting a piece out of a circular ring, in the usual manner; then in heating portions of said ring, including said ends and sections anterior thereof, to a degree of temperature capable of rendering said heated portions ductile; and then, while in a ductile state. shaping said portions, as over a mandrel, to give them, equally, a distorted contour; wherein the ends aforesaid are inclined inwardly and said end portions caused to describe a segment of a circle whose diameter is slightly less than't-he diameter of the untreated ortion of the ring in its free state, The s apin operation aforesaid, effects a distortion 0 the ring from a true circle;

which distortion, upon cooling of the ring.

becomes thereof.

The rin as distorted, and while in a free state, is o slightly less diameter in a medial line drawn from between its ends to the heel of said ring, that diameter graduating out to merge into the normal diameter of the non-distorted portion of the ring in its free state.

The degree of distortion aforesaid is governed by the extent of the space separating the ring ends in its free state, which regulates the circle restoratory movement of the free ri portions in the contraction of the ring to its operative, cylinder fitting condition; in which it is requrcd to have a true cylindrical contour. In this contractcd state, the expansive effort of the ring causes it to exert outward, radial bearing, in which permanent as to the free state the face of said ring. throu 'hout its entirepermit contraction.

end portions, and

crnni; and while ductile, is pressed against :1 form or mandrel whose contour is of up propriatc character.

1 have found that rings of ordinary cast iron, shaped while ductile to the requisite, described distortion, are possessed of adequate resiliency to fulfil their functions in service. Also, it may be stated that vanadium iron gives good results; and, undoubtedly, other alloys'niay be satisfactorily employed.

Other features and advantages of my'said invention will hereinafter appear.

In the drawing Figure 1 is a plan view of a circular ring from which a section has been removed to Fig. :2 is a similar View, showing the ring upon a mandrel, and one end portion thereof, rendered ductile by heat, pressed against the mandrel to distort its shape,

Fig. 3 is a similar view of the ring, as partially treated, and fitted within a cylinder, and

Fig. 4 shows the ring, as treated at both fitted within a cylinder.

In carrying out my improved method of producing piston rings, I take an annulus,

as 1, of cast or other metal having adegree of elasticity suitable fOItllB purpose, and of oversize; that is to say, the outsfle diameter of the annulus is greater th 11 the inside diameter of the cylinder for which it is annulus to thus leave the opposed ends 2, 3, separated by a space whose extent allows the contraction of said annulus to the desired, tensional, cylinder fitting area. Then the annulus is heated, over the ends and portions 4, 5, thereof, representing the portions, anterior, respectively, to the ends a, 3; and finally said portions are shaped, while ductile, out of the circular form of the annulus, as over a mandrel 6; whereby the ends 2, 3, and the anterior portions 4, 5, are

I then remove a section of saidcaused to become permanently inclined inwardly, to describe, in the free state of the ring, a segment of a smaller circle.

'1 lie efi'ect of the distortion described, when the ring is contracted, so as to bridge the space separating its ends and fit with radial tension within its cylinder, is to allow the ring to assume a true circular contour over its entire circumference.

Variations may be resorted to within the spirit and scope of my claimed invention.

I claim:

1. T he method of producing a. piston ring consisting in treating a, metal annulus by' localized heat and pressure whereby it is permanently distorted in a free state, said distortion enabling said annulus to assume a true circular contour in a contracted state.

2. The method of imparting even circumferential radial bearing to a piston ring in a state as contracted from its free circular form, the same consisting in heating the ring end portions to render them ductile, and then in distorting said end portions out of the circular contour of said ring, the character of such distortion permitting said ring, when contracted, to possess true circular form;

3. The method-of making piston rings which consists in producing an annular blank, removing a section of said blank to provide opposed spaced ends, andinpermanently distorting the end portions only of the blank, by inclining them inwardly, the character of said distortion-enabling said blank, when contracted for service tension,

to possess true circular contour.

Signed at the borough of Manhattan, in the city, county and State of New York, this 14th day of April, A, D. 1616.

MILLAR-D L. DUNHAM.

\Vitnesses:

W. E. FEE,

'F. W. BARKER. 

